The term "polyphenylene ether resin" includes a family of polymers well known to those skilled in the art, they are made by a variety of catalytic and non-catalytic processes from the corresponding phenols or reactive derivatives thereof. By way of illustration, certain of the following polyphenylene ethers are discussed in Hay, U.S. Pat. Nos. 3,306,874 and 3,306,875, and in Stamatoff, U.S. Pat. No. 3,257,357 and 3,257,358. Also, the Bennett and Cooper patents, U.S. Pat. Nos. 3,639,656, 3,642,699 and 3,661,848 describe processes for the preparation of polyphenylene ethers. In the Hay patents, the polyphenylene ethers are prepared by a oxidative coupling reaction comprising passing an oxygen-containing gas through a reaction solution of a phenol and a metal-amine complex catalyst. Other disclosures relating to processes using metal-amine catalysts are found in Bussink et al, U.S. Pat. No. 3,337,499; Blanchard et al, U.S. Pat. No. 3,219,626; Laakso et al, U.S. Pat. No. 3,342,892; Borman, U.S. Pat. No. 3,344,166; Hori et al, U.S. Pat. No. 3,384,619; Faurote et al, U.S. Pat. No. 3,400,217; and disclosures relating to metal based catalysts which do not include amines, are well known from patents such as Wieden et al, U.S. Pat. No. 3,442,885 (copper-amidines); Nakashio et al, U.S. Pat. No. 3,573,257 (metal-alcoholate or phenolate); Kobayashi et al, U.S. Pat. No. 3,455,880 (cobalt chelates); and the like. In the Stamatoff patents, the polyphenylene ethers are produced by reacting the corresponding phenolate ion with an initiator, such as a peroxy acid salt, an acid peroxide, a hypohalite, and the like, in the presence of a complexing agent. Disclosures relating to noncatalytic processes, such as oxidation with lead dioxide, silver oxide, etc., are described in Price et al, U.S. Pat. No. 3,382,212. All of the patents which are mentioned above are incorporated herein by reference.
The Cizek patent, U.S. Pat. No. 3,383,435 discloses blends of polyphenylene ether resins and styrene resins. The thermoplastic blends disclosed by Cizek may include a rubber-modified styrene resin, as well as crystal polystyrene. This patent is also incorporated herein by reference.
It has been observed that blends of polyphenylene ether resins with styrene resins exhibit a discoloration when exposed to ultraviolet radiation. The discoloration is usually in the form of a yellowish tint that is encountered even upon exposure to ordinary fluorescent lights or to sunlight. Higher concentrations of polyphenylene ether in a particular composition will result in a more rapid yellowing of the test sample.
It has been discovered that the use, in combination, of a stabilizer which comprises a hydroxybenzophenone or a hydroxybenzotriazole with an organic nickel compound provides a stabilized polyphenylene ether-styrene resin composition.
Certain stabilizer compositions within the scope of the invention show a higher degree of stabilization than would be expected from the behaviour of either component alone.